


Catty Catty's Cutie Catti Cat

by eternalflamebabby



Category: Deltarune (Video Game), Undertale (Video Game)
Genre: Age Play, Diapers, Fluff
Language: English
Status: In-Progress
Published: 2020-10-26
Updated: 2021-01-23
Packaged: 2021-03-09 06:20:35
Rating: General Audiences
Warnings: Creator Chose Not To Use Archive Warnings, No Archive Warnings Apply
Chapters: 3
Words: 4,085
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/27209530
Author URL: https://archiveofourown.org/users/eternalflamebabby/pseuds/eternalflamebabby
Summary: Catti is growing up fast and big sister Catty misses spending time with her baby sister. Maybe a fun movie night is just the trick!(Catti... Catty... get ready to get confused!)Note: Diapers and ageplay.
Comments: 4
Kudos: 10





	1. Chapter 1

QC’s Diner was a mess. As usual. 

The pile of miniature cake wrappers near -- but not in -- the trash can suggested Bratty had finally had her fill; something she would later regret. As usual. 

The still slowly spreading puddle of water by the ice tray was no doubt on account of Fuku Fire getting too close to the drink section. Again. 

And Temmie would inevitably come storming back through as soon as they realized they’d left EG on the counter. Again.

“Nope,” Catti muttered to herself, expression muted as ever. The white furred, yellow-eyed, goth cat could not be bothered to muster as much as a shrug as they turned their back on QC’s Diner.

Having clocked out not a minute too soon, QC’s Diner was now officially someone else’s problem. Catti could only guess as to whose problem it now was, as her replacement shift hadn’t arrived yet. But, far as Catti was concerned, that wasn’t her problem either. Not anymore, anyway.

It did make the wait out front for her ride home rather awkward, however. Catti was making every effort to keep her eyes glued to her phone. She was hoping to avoid making eye-contact with the people who had just gone into the diner as she stood a few feet away from the entrance -- and praying they wouldn’t notice her waitressing uniform.

Her older sister, Catty, wasn’t making things much easier. There was no response to any of the text messages that Catti had sent; forcing her to stare at a blank phone screen while she pretended to have a text conversation with nobody. Which meant Catty was either on her way -- and busy driving -- or had forgotten about Catti’s shift and fallen asleep on the couch again. Only time would tell.

“Late again,” Catti sighed. 

She couldn’t wait to get her license. Not having to deal with her overly-enthusiastic sister picking her up from work every other day would be a welcome relief. While the older sibling’s big hearted hugs are undeniably genuine, some would suspect that Catty enjoyed embarrassing and smothering her little sister with affection in equal measure.

*BZZT*

Catti’s phone vibrated the all-too-familiar hum of a text message as the screen lit up in a soothing glow. And with it, the promise of ever-present escapism and a text that read:

“LIKE, LOOK UP!”

Catti, who had been effectively ignoring her surroundings, peeled her eyes from her phone and peered ahead. Parked right across from where she had been standing was Catty, still inside their car, waving one paw enthusiastically while the other one honked the horn in celebratory fashion.

Catti greeted her older sister with a monotone “Hey,” as they closed the car door behind them. Her nose once again aimed at her phone.

“And, like, how’s my lil’ sis doing,” said Catty, in her usual bubbly way. The lavender-furred feline was practically bouncing in the driver’s seat, eager to hear about her baby sister’s day.

Catti, however, was not feeling very chatty. Especially given the fact she’d spent all day at school and then straight to work. Refusing to meet Catty’s gaze, Catti could feel her older sister’s big yellow eyes burrowing into the side of her skull. 

This had become routine as of late. The daily efforts of Catty to get something, anything, out of Catti; while Catti herself would doggedly refuse to give so much as an inch. Catty loved her little sister, but had grown concerned about their lack of friends and social skills. Whereas Catti felt that Catty had increasingly become an invasive force in her life, pushing her to do things she otherwise would not. It was, after all, at Catty’s insistence that Catti got her job at QC’s Diner.

Nonetheless, Catti remained determined to out-stubborn her big sis. She offered a non-committal, “Okay, I guess,” in the hopes of appeasing the somewhat overbearing sister and finally be off on their way.

A few uncomfortable seconds later, Catti’s prayers were finally answered. She heard the car roar to life as Catty stepped on the gas with a sigh and a somewhat dramatic rolling of her eyes to go along with it. Stopping short of speaking out loud, Catti thought to herself, “Finally.”

Tapping on her phone, Catti hoped to get her mind off of her long day. Maybe she could get Jockington to send her some “cool” sports memes. Heck, even Temmie would be acceptable; and Catti had good reason to text them on account of how they had forgotten EG back at the diner. And maybe it *was* a bit mean to just leave EG there. After all, they hadn’t hatched yet. Who knows what sort of trouble an unsupervised egg could get into.  
“By the way-” Catty spoke up, refusing to let the silence linger for too long, “Dad’s gonna be, like, really late. So I got some movies and thought we could have, like, a girls night,” Her pitch peaking by the end of her sentence, enthusiasm plain for all to see.

And just like that, Catti’s plans of locking herself in her room to spend an evening away from people were now at risk of being delayed or disappearing altogether. It was bad enough being robbed of their entire day with school and work. Having what little time they had to themselves interfered with was worse than a grounding in her mind. “Can we… not?”

“Aw, c’moooon,” Catty whined, half-jokingly, half-serious. “We never spend time together anymore! I miss my baby sis!” Her smile remained unflinching, but the joviality draining from her voice into a more somber tone was not hard to miss. As different as the two siblings were, they did have *some* things in common. More than most people would think.

“Fine,” Catti relented with a long drawn out sigh. The weekend was coming up after all, and she’d be able to stay cooped up in her room for two days straight if she wanted. And a thought popped into Catti’s mind. Maybe she could get a long weekend out of this exchange.

“Can you... get me out of school tomorrow,” she asked plainly, “And maybe work?”

The car came to an abrupt halt. It was sudden enough that Catti’s phone nearly flew out of her paws. It was barely a second later that she noticed Catty gawking melodramatically in Catti’s direction. 

“You want me to LIE,” Catty gasped, paws firmly planted on the sides of her face as if aghast at the mere suggestion. The playfulness in her big yellow eyes were an obvious giveaway that she was being over-the-top for funsies, and not at all serious.

Making every effort not to smirk, Catti’s yellow eyes betrayed her own amusement all the same; even as she rolled them off to the side. She knew her big sister was no saint either. And usually these overly-sarcastic responses were Catty’s way of getting on board with whatever shenanigans may have been suggested. 

“Deal,” said Catty, with a firm nod. Catti thought this was surprisingly decisive for her big sis. “You do what I say, and I’ll, like, make up some excuse to get you out of school tomorrow!”

“And work,” Catti added for emphasis.

“And work, yes,” Catty rolled her eyes, as if it were obvious she would do that.

“But you gotta, like, do *everything* I say, or no deal. Got it?” 

Catti felt a tinge of concern at that last stipulation by her sister, but shook it off in short order. One evening for a whole day off -- nay, a long weekend -- was a pretty sweet deal. And for whatever sibling rivalry they may have from time to time, Catty had never done anything outright mean-spirited or intentionally hurtful.

Making every effort not to betray any enthusiasm, Catti gave a firm nod, and said, “Got it.”

The rest of the drive home was uneventful. Catty hummed happily to herself while she drove, and Catti welcomed the relief of being able to just tune out the world for a little bit on the ride home. Having appeased her big sister meant she would be content for the rest of the trip home.

Catty parked the car in the driveway upon their arrival and, turning to Catti, said, “Alright, I got, like, some stuff in the back. I want you to head straight upstairs and wait for me, okay?”

Catti nodded nonchalantly, eyes still on her phone. She was already tuning her sister out for whatever boring movie night she might have planned.


	2. Chapter 2

Catti looked in the mirror.

She could tell from the reflection of the bathroom window that it was getting dark out.

Normally the gothy cat would have hunkered down in her bedroom by now, but their big sister, Catty, had roped them into a girls movie night or somesuch.

The deal being that said big sister calls both work and school to get Catti a day off; and a long weekend with it.

What Catty wanted out of this exchange, however, Catti could only guess. Most likely some household chore, she thought to herself. Laundry or cleaning the bathroom -- something neither of them would be inclined to do. 

It didn’t matter much what the purple cat had in store for her younger sibling. One evening of chores for a long weekend was a pretty good trade, no matter how you sliced it.

Catti had already peeled off her work clothes, the only reminder left of her slog of a part time job. She admired herself briefly in the mirror. Wearing her favorite purple tank-top and her bunny skull undies, her dark mood had finally begun to improve. 

She briefly considered trying to weasel her way out of whatever her big sister had planned, but decided against it just as a knock on the bathroom door snapped her out of whatever plot she might have potentially considered.

“Catti,” the voice from the other side yelled, “are you, like, in there?”

Catti stared at herself in the mirror, as if waiting for her reflection to come up with some clever retort. Not getting any kind of response, the dark-haired cat took a deep breath and grumbled, “Yeah.”

“Can you, like, let me in?” It was Catty. Of course.

Catti rolled her eyes at the door -- positive her sister would know, regardless of whether they could prove anything -- and asked, “Why?”

“So we can get you ready for your bath, you goober!”

Catti blinked a few times at her reflection, as if wondering if they had both heard the same thing.

Catty stood on the other side of the door, waiting expectantly for her little sister’s response. Not sure if her baby sister had heard them correctly she reiterated her request, “I said, like, we need to get you ready for your-”

The bathroom door slowly crept open, one exhausted looking yellow eye peering through.

“What?”

“It’s bath time, silly!” Catty enthusiastically waved a towel and shampoo at her sister. She added for emphasis, “I even got the bubble bath you like!”

Catti’s eyes widened for a split second -- betraying perhaps a hint of amusement -- before composing herself once more. A subtle expression that was not lost on her older sister. Nonetheless, the goth cat twitched her nose ever so slightly, rolled her eyes (this time in plain view of her sister) and said, “I’m not a baby anymore.” 

She motioned to close the door once more, when one purple paw slipped in, holding it in place.

“*Everything* I say,” Catty reminded her sister, a devious grin creeping its way onto her face, “Or, like, no deal.”

Catti would stare in slight disbelief for a few moments, pondering just what her big sis was up to. Chores was what Catti had been expecting. Or something otherwise annoying or time-consuming to do. A bubble bath was most certainly not on the list of things she had considered would be on the agenda for this evening.

Catti eyed the towel and shampoo, and then looked back at her sister. “I... don’t get it,” she said dryly. A statement that was less capitulation and more honest inquiry. 

“I told you,” Catty explained, “I, like, miss my baby sister!”

The words lingered in the air briefly before it finally began to dawn on Catti what was happening.

Even as her face remained expressionless as ever, Catti’s eyes betrayed her feelings yet again, darting away from her sister. Memories of fun childhood bath time with her big sister bubbled up to the surface. 

“C’mon,” Catty pleaded, “It’ll be fun, I promise!”   
“Promise?” Catti side-eyed her sister, seeking some reassurance, unsure what to make of things still.

“Pinky swear!” Catty stuck one arm though the door, pinky out. 

Catti raised one eyebrow at her over-eager big sister. What was the worst that could happen? Catti figured she could always bail at any time and just go to school the next day. And if she *did* have fun, then wouldn’t that be a win-win?

Besides, Catti *did* miss being the baby sister on some level. Not having to worry about school or work. No longer having her big sister dote on her. These were things she’d done away with in part due to the expectations of budding adulthood; and also in part due to her own youthful teenage rebellion.

Maybe maturity was less about doing “adult” stuff, and more just doing what you want, regardless of what people think. 

Alas, Catti barely had any time to ponder this line of thought before her sister impatiently barged into the bathroom, curled their pinkies together, and announced, “There! It’s, like, a promise!”

Catti let out a heavy sigh. There was no arguing when Catty got like this. Fighting would only delay the inevitable. 

A deal was a deal, after all. 

And a pinky swear was an unbreakable oath.

“Fine.”

No sooner had the word dryly escaped Catti’s lips had her sister begun running the bath, bubbles beginning to froth. Sticking one paw to measure the water, Catty gestured towards her baby sister with her other arm, “You should, like, take those off.”

All of a sudden Catti felt incredibly self-conscious about her body. Her face must have done one of those things that were immediately obvious to no one but Catty, because her big sister rolled her big yellow eyes in her usual mockingly-dramatic fashion and said, “It’s nothing I haven’t seen before, you fuzzy goofball!”

Not getting much of a response from her kid sister -- who was making every effort to avoid eye contact -- Catty smirked and inquired, “Does my baby sister need help getting out of her clothes?”

“No!” 

Catti was already halfway removing her top when she blurted the word out in the most notable show of emotion in days. One quick kick and her favorite bunny skull undies were halfway across the floor. She could feel herself blush from embarrassment. The gothic cat girl could not remember the last time her big sister, let alone anyone, had seen her naked.

“Good job,” Catty praised her little sister nonchalantly. The bubble bath was beginning to spill over the top of the bathtub. Paying it no heed, Catty sat herself next to the bathtub. Waiting expectantly for her little sister to get in, she instructed, “Now, like, get in!” 

Catti did as told. Shuffling over she could feel the warmth as she neared the tub. Stepping over, Catti dipped one tentative toe. 

“In you go!”

Done with waiting, Catty swiftly dunked Catti into the sea of bubbles and began scrubbing. Catti opened her mouth to complain but got little more than a frothful of bubbles for her efforts. Ultimately, a low growl was as much as Catti could muster to communicate her displeasure.

“Oh stop,” Catty shushed her little sister, “You were, like, taking forever!”

Catti crossed her arms in futile defiance. Catty, undeterred, massaged some shampoo into the gothy cat’s hair, saying, “Close your eyes.” 

As the bath went on -- and in spite of herself -- Catti began to purr contentedly. Catty made no comment. Perhaps feeling that she’d teased her baby sister enough, the purple cat girl chose to let good enough be.

Just as Catti was getting used to this, the bath was over, and Catty was drying off her baby sister with the towel she had brought in earlier.

“See,” Catty finally spoke up, “That wasn’t, like, so bad. Right?”

Catti gave a non-commital shrug, but her big sister knew better. Catty wrapped the towel around her little sister -- content that fun had been had in spite of grumbles -- and said, “And now that you’re, like, fresh and clean, we can get you in a nice nappy!”

Catti blinked, unsure if she had heard correctly.

“What?”


	3. Chapter 3

“No.”

Catti furrowed her brow, arms crossed.

“Yes.”

Catty wiggled her eyebrows, smiling as she waved a thick nappy in front of her sister. Catti, unflinching, and in spite of herself, couldn’t help but notice the cute dinosaur print. She used to like dinosaurs as a kid.

“Everything I say,” Catty reminded Catti with a grin. “Remember?”

The gothier of the siblings felt ambushed and with little recourse. Turning her face askance, she protested nonetheless, “You didn’t say anything about diapers.”

“You, like, didn’t ask,” the purple cat smirked; confident in having cornered her sister with the perfect sibling comeback.

Catti was unmoved. This was already more than she had bargained for; and with no idea where this was headed, there was no telling what else the older sister had in mind.

“Like, if you really don’t wanna…” Catty sighed, a hint of disappointment on her face. 

“But, like, deals off!”

Catti barely flinched in relief. But visibly winced at the latter part. The whole point of this was to get a long weekend to herself. Unexpectedly Catti found herself debating whether or not one evening of humiliation was worth it.

Thinking she could follow through with some assurances, Catti shot her big yellow eyes at her sister and demanded, “No one finds out.”

“EVER.”

Catty blinked. Perhaps she was surprised at her little sister’s change of mind. Or perhaps she didn’t consider that word getting out would even be a concern on their part.

“I’d, like, never do that,” Catty insisted.

“Swear.” Catti glared.

“Like, cross my heart!” Catty raised one paw, the other one criss-crossing across her chest, with a stern nod to punctuate it.

“Pinky swear.” Catti said flatly, paw out, pinky in the air.

“Pinky swear!” Catty locked her pinky with her gothy sister’s and shook their paws in agreement.

“Fine.” 

Catti was still wary of her sibling, but chose to trust her nonetheless. And the black and white cat could always back out if it got too weird, she thought to herself.

“Besides,” Catty said chipperly. “It’s not like I haven’t changed your diapers before,” she added with a playful wink.

The normally unflappable Catti could feel her face blush, flustered at the notion of ever having been that young. She was a goth rebel, after all. Anything kiddy or childish was an embarrassment to her now. If her older sister was trying to get Catti out of her comfort zone, it was working.

“Don’t worry,” Catty reassured, “your big sis has got it all under control.”

Ushering her baby sister out of the tub with one guiding paw, Catty was finally in control. For now, anyway. The purple-furred cat was amazed she’d gotten this far with her obstinate sibling. Maybe her plan would work after all.

A quick drying by towel and hair-dryer and Catti was left fluffy as can be -- much to her chagrin. Catty made no effort to tease her kid sister, uncommon as that may be. Choosing instead to simply hum a happy tune while brushing Catti’s hair. One could even say the older sister was quite enjoying herself.

Perhaps still in a daze from the warm bath, or numbed by the grooming, Catti barely took notice of when she arrived in her bedroom, wrapped in a bright blue towel. The black and pink walls littered with posters of metal bands she liked were unmistakably hers. Not many folks would spend weeks arguing with their parents to let them paint their bedroom walls black, but Catti did.

“Wait here.”

Catty sat her younger sibling on the edge of the bed. It had fuchsia leopard print covers and zebra print pillow covers. Tacky hand-me-downs that surprisingly fit Catti’s off-beat aesthetic. 

“Back!” Catty had somehow materialized back into the room, several objects in her arms, some Catti could immediately recognize. Specifically the diapers and baby bottle. The goth cat hoped the two would be for purely aesthetic purposes, but Catti suspected her older sister might get a smidge carried away; as they would often do.

“Now, like, lie down for me,” Catty urged, as she unfolded a thick diaper in front of her kid sister. “Your big sis has got it all under control.”

Catti was hesitant, but did as told, clutching the towel as the only form of modesty left to her. 

“Like, relax.”

Catty could tell that their often despondent sibling was feeling anxious. Undeterred, the older sibling shooed away Catti’s grip on the towel and unwrapped the goth purrito. 

They typically talkative Catty was strangely calm -- and very much in control -- as they gripped Catti’s lower hind legs by the ankles with one paw. It happened so suddenly, that even the laconic Catti let out a short yelp of surprise. With nary a word, Catty slid a big puffy diaper beneath her baby sister’s bottom, and gently lowered Catti’s behind onto it.

The scent of baby powder soon wafted around the room, as Catty generously shook the bottle all around Catti’s lower half, a good bit of it landing on her thighs and belly. The dry chalky powder made the goth cat’s nose twitch uncomfortably, and she soon found herself turning her face away and squinting.

“Sorry,” Catty apologized. “Guess I, like, got a bit carried away,” she added dusting off what she could. But the damage was already done, and not much could be done about it.

Spreading Catti’s legs, Catty pulled the thick padded diaper up and over and began to attach the tapes one by one, ensuring they stuck properly and had a tight fit around the waist. Once the tapes were in place, the purple cat patted her broody sibling on the bum and asked, “So, like, how does it feel?”

Catti sat up, inspecting her sister’s handiwork, and dusting off what baby powder she could. Embarrassment had somehow turned into curiosity, and trying to put into words the sensations she was feeling -- as best she could, anyway.

“Cozy,” Catti expressed rather dryly. 

“I’ll take it,” Catty said excitedly. “Now let’s, like, get downstairs and watch some cartoons!”

Catti side-eyed her older sister, and asked “Like this?”

Catty tilted her head briefly, as if puzzling out the question.

Catti gestured at her body, naked with the exception of a diaper.

“Oh,” Catty spoke up in realization, “I, like, know just the thing!”

Digging through Catti’s drawers without so much as asking -- and a familiarity that made Catti question if her missing socks and underwear were Catty’s doing -- the older sister pulled out a frilly black babydoll dress with pink bats. Something Catti had gotten for Halloween but never actually wore.

Catti sighed, in part out of relief that it wasn’t anything more embarrassing, and in part glad to be going downstairs semi-decent, at least.

Catty managed to pull the dress over her kid sister’s head without much fuss. Having dressed Catti as a kid in the past they both instinctively did as they would when younger. Catti stuck her hands up for Catty to direct through the puffy sleeves, and tugged on the dress to pull it over the rest of her sister’s body.

Almost as if by the same instinct, Catti huffed and crossed her arms. Whether the goth cat was trying to appear annoyed or defiant, Catty didn’t quite care. The older sister was too busy cooing over her cute little sister’s look for the evening.

“You’re soooo cuuuuute!” 

Catty pinched Catti’s cheek, adding, “Even with your big grumpy face.”

Catti took a deep breath and reminded herself of the deal that was made. Anything Catty wanted, in exchange for a long weekend. 

And if it meant getting literally pampered by her big sister for one night, then maybe this wouldn’t be so bad after all.

“Whatever,” Catti huffed.


End file.
